An injection valve (injection nozzle) is a valve, which on an internal combustion engine, such as a spark-ignition or a diesel engine, injects fuel into the intake tract via port fuel injection (PFI) or into the combustion chamber via direct fuel injection (DI) of the internal combustion engine in order to drive the motor vehicle. In direct fuel injection the injection valve injects fuel directly into the combustion chamber of the internal combustion engine, whereas in port fuel injection, mixture formation takes place not in the combustion chamber, but upstream of the injection valve, for example downstream of a throttle valve.
US 2014/0116393 A1 discloses a system having an injection valve for injecting fuel into a cylinder of an internal combustion engine. A main cooling line is provided, through which coolant can circulate through the internal combustion engine. An auxiliary cooling line is also provided, which connects the main cooling line and carries coolant to the injection valve.
U.S. Pat. No. 8,078,386 B2 discloses a method for controlling the fuel supply to an internal combustion engine, which can be operated by means of port fuel injection and direct fuel injection. A second type of fuel is fed from a second tank to a direct fuel injection valve and a first type of fuel from a first tank to the port fuel injection device. In response to an unsuitable fuel, the first type of fuel from the first tank is fed to the direct fuel injection valve. In response to the receipt of an incorrect supply signal, the direct fuel injection can be supplied with the second type of fuel. By supplying at least some fuel of the other type to the direct fuel injection valve, it is possible, under various conditions, to use fuel to cool the direct fuel injection valve.
U.S. Pat. No. 6,718,954 B2 discloses a device for cooling fuel by means of a cold side of a thermoelectric unit before the fuel enters fuel delivery components, such as injectors, carburetors and throttle valves, for example. An excess of cooling energy is sufficient to cool the fuel delivery components, so as to supply a cooling buffer and prevent a reabsorption of heat once the fuel has been cooled. The warm side of the thermoelectric unit is cooled by a second cooling liquid system distinct and separated from the main cooling fluid system for the engine block. Excess fuel is led through a fuel bypass pressure regulator to a fuel bypass line, and the excess fuel becomes cooling liquid, which is returned to a fuel tank.
US 2008/0196700 A1 discloses a fuel cooling system for a diesel engine having a row of cylinders, a fuel tank, and a common-rail fuel injection system. The system comprises a fuel distributor circuit for delivering fuel from the fuel tank to the cylinders, a fuel recycling circuit recycling uninjected fuel, a temperature sensor for registering the fuel temperature, a fuel coolant heat exchange system for cooling the fuel, a coolant reservoir, an electrical coolant pump, and a heat exchange distributor also being provided. In addition, a mechanism is provided for controlling the electrical coolant pump operation, together with an air coolant heat exchange system, which is coupled to the fuel coolant heat exchanger system for cooling the fuel. In order to cool the coolant, the air coolant heat exchange system is exposed to vehicle ram air. In addition, a heat exchange distributor and a fan are provided, together with a mechanism for controlling the fan.
US 2010/0084489 A1 discloses a control arrangement for a fuel injection device. A leakage path ducts leakage fuel originating from an inlet to a fuel drain connection. The control arrangement comprises an individual tank, which supplies the inlet, and comprises a coolant connection to a plurality of injection valves, and collects fuel from the fuel drain connection of the plurality of injection valves.
U.S. Pat. No. 8,056,537 B2 discloses an internal combustion engine, such as a diesel engine with direct fuel injection. The injection valve according to U.S. Pat. No. 8,056,537 B2 comprises a first and a second inlet together with an actuator assembly for valve actuation. A cooling system for cooling the actuator assembly, which is coupled to a fuel system, is furthermore provided. The cooling system is designed to carry cooling liquid via a heat exchange surface of the actuator assembly, in order to exchange heat energy.
DE 11 2004 000 701 T5 (U.S. Pat. No. 7,021,558 B2) discloses an injection valve for injecting pressurized fuel into a combustion chamber of an internal combustion engine. A nozzle valve element has a longitudinal passage, which has an outer end for draining off a cooling liquid flow and an inner end for receiving a cooling liquid flow. The nozzle valve element furthermore has a transverse passage, which is situated next to the inner end of the longitudinal passage and extends transversely between the longitudinal passage and the nozzle bore. In operation, a quantity of coolant flows into the nozzle bore, through the transverse passage into the longitudinal passage and along the longitudinal passage in order to cool the nozzle valve element.
Dual-fuel vehicles are also known, in which two different fuels are fed to the internal combustion engine, the internal combustion engine being operated for a while with the one fuel and for a while with the other fuel. This may be, on the one hand, conventional gasoline or diesel fuel. On the other hand, this may be a gaseous fuel. The vehicle can thus be operated with the conventional fuel if the gas tank is empty and it is not possible to reach a refueling station. The range of the vehicle is thus extended compared to vehicles powered by gaseous fuels alone. The conventional fuel is conveniently injected directly into the combustion chamber, whilst the gaseous fuel is introduced into the intake tract. In this respect in a motor vehicle of flexible-fuel or also dual-fuel design or in a motor vehicle having an internal combustion engine which is operated both with port fuel injection and with direct fuel injection to the internal combustion engine, a flow of conventional fuel through the injection valve does not always ensue, so that there is no flowing fuel to exert a cooling effect on the injection valve. Since the injection valve for direct injection of the conventional fuel is inoperative due to operation of the internal combustion engine on the gaseous fuel (that is to say CNG, LNG, methanol, ethanol, natural gas, for example), there is therefore no fuel flow passing through it. If the injection valve is not cooled, the temperature not only at its tip but also on the seals may exceed a limit, with the resulting in operational malfunctions. Moreover, there may still be fuel present in the injection valve which is exposed to the considerable thermal load. Thus the retained fuel may warm up and under the effects of heat may crack and/or vaporize, that is to say evaporate, which naturally depends on the prevailing pressure ratios and temperature conditions.
The inventors herein have recognized the above issues and identified an approach by which the issues described above may be at least partly addressed. The object of the disclosure is to provide an injection valve for an internal combustion engine of a motor vehicle which comprises a cooling device affording an improved cooling effect.
In one example, the above issues may be at least partly addressed by a an injection valve for an internal combustion engine of a motor vehicle comprising: a cooling device for cooling the injection valve, wherein the cooling device is a thermosiphon cooling device comprising a reservoir volume, and a cooling element of the cooling device having a thermally conductive connection to the reservoir volume. The injection valve used for injecting conventional fuel directly into the combustion chamber comprises the thermosiphon cooling device.
The thermosiphon cooling device is a closed cooling system without the requirement of a pump. A circulation of the cooling medium, in this case fuel, that is to say liquid fuel such as diesel fuel or gasoline, is produced solely under the effect of gravity. The lower specific density of the warmer medium makes it lighter than the colder medium, so that the warmer medium rises to the top and the colder medium sinks to the bottom. Since the internal combustion engine is being operated in the gas mode, the cooling medium, that is to say the gasoline or diesel fuel, in the inoperative injection valve is warmed and therefore becomes lighter. It therefore rises to the top of the injection valve. There the cooling medium is cooled and therefore becomes heavier. It sinks down towards the tip of the injection valve and the whole process is repeated. The advantage of the thermosiphon cooling device is the simple construction without a pump. Furthermore, a gravitational circulation of the cooling medium can ensue even without any admission of the coolant (without any admission of fuel), and bring about cooling. It is therefore possible to cool even an inoperative injection valve, that is to say one not in operation and therefore without a flow of cooling fuel passing through it.
According to the disclosure, the thermosiphon cooling device comprises a reservoir volume. A first line inside the injection valve is connected to a fuel supply. The warmed fuel can rise in the reservoir volume, whilst at the same time the cooled fuel is able to sink again. It is practical here if the cross section of the reservoir volume, which may also be referred to as a ring line, is adapted so as to allow a simultaneous rise and fall.
The first line and the reservoir volume are arranged concentrically with one another. This arrangement affords a particularly good thermal coupling, especially of the reservoir volume in the compact design form of the injection valve. This again improves the cooling effect of the cooling device. The reservoir volume has a medium-carrying connection to the first line. It is advantageous if the first line is connected to the reservoir volume in the area of the tip of the injection valve. Also, an additional fuel line may be included to enhance flow of fuel (due to thermosiphon effect) from the lower part of the injection valve up to the upper part of the valve, wherein the reservoir volume is located in the upper part. The reservoir volume suitably encloses the first line like a jacket.
It is also possible to cool the reservoir volume externally, for which purpose it is possible to use the coolant of the internal combustion engine, for example. The reservoir volume is advantageously arranged peripherally inside the injection valve with its outer wall close to an outer circumference of the body. The reservoir volume is therefore also able to dissipate heat energy outwards, which affords improved cooling of the fuel and thereby assists the cooling effect of the cooling device.
In one example, the injection valve comprises at least one cooling element, which has a thermally conductive connection to the thermosiphon cooling device, which is the reservoir volume. This again improves the cooling of the fuel and likewise assists the cooling effect of the cooling device. In another example, the cooling element may comprise fins, which are arranged externally around the injection valve (around the circumference of its body). The fins increase the effective surface of the injection valve, so that the cooling effect for cooling the warm fuel in the reservoir volume is further improved.
In yet another example, the upper area of the injection valve may be actively cooled by coolant. For this purpose, fuel from the fuel tank may be supplied as coolant. In particular, it will be possible to bring coolant from the internal combustion engine, so that the upper area, possibly together with the reservoir volume, and/or also the fins, and/or the outer area of the injection valve are cooled by the coolant.
Although the development according to the disclosure serves to cool the fuel in the inoperative injection valve to an extent, the development according to the disclosure represents a cost-effective means of cooling the fuel retained in the injection valve, the cooling being sufficient to prevent critical values of the retained fuel. The device may obviously also be working when the injection valve is operative. This is especially the case since the connection of the first line to the reservoir volume is maintained at also times, that is to say both in the inoperative state and in the operative state. Thus the injection valve with the arrangement according to the disclosure can also be cooled in the operative state. This has a positive effect on the fuel consumption and on the performance of the internal combustion engine.
The disclosure is particularly advantageous in dual-fuel vehicles, in which two different fuels are fed to the internal combustion engine, the internal combustion engine being operated for a while with the one fuel and then for a while with the other fuel. This may be, on the one hand, conventional gasoline or diesel fuel. On the other hand, this may be a gaseous fuel. The vehicle can thus be operated with the conventional fuel if the gas tank is empty and it is not possible to reach a refueling station. The range of the vehicle is thus extended compared to vehicles powered by gaseous fuels alone. The conventional fuel is conveniently injected directly into the combustion chamber, whilst the gaseous fuel is introduced into the intake tract. In this respect in a motor vehicle of flexible-fuel or also dual-fuel design or in a motor vehicle having an internal combustion engine which is operated both with port fuel injection and with direct fuel injection to the internal combustion engine, a flow of conventional fuel through the injection valve does not always ensue, in which case there is no flowing fuel to exert a cooling effect on the injection valve. Since the injection valve for the direct injection of the conventional fuel is inoperative due to operation of the internal combustion engine on the gaseous fuel (that is to say CNG, LNG, methanol, ethanol, natural gas, for example), there is therefore no fuel flow passing through it. With the disclosure, however, the inoperative injection valve, that is to say the fuel retained therein, is sufficiently cooled.
It may be pointed out that the features and measures individually cited in the following description may be combined with one another in any technically appropriate manner and may set forth further developments of the system. The description additionally characterizes and specifies the disclosure particularly in conjunction with the figures.